When the axis of angular rotation of a radial arm saw is located in spaced relationship to a plane defined by the relatively stationary work fence, the fence will be intersected by the rotating saw blade at various points along the fence, depending upon the angle of cut. When such a saw is employed for the mass production of truss lumber or the like, the fence is soon cut at so many locations that its strength is lessened and it may represent a hazard to the sawyer, particularly while cutting short material.
Accordingly, the objective of this invention is to provide an arrangement in a radial arm saw to automatically shift the work-engaging fence along a linear path in one direction or the other automatically in response to angular displacement of the saw and its turntable about the vertical axis of rotation of the saw and turntable. Such automatic linear displacement of the work fence relative to the rotational axis of the saw turntable eliminates cutting through the fence at multiple points while sawing at different angles and causes the saw blade clearance gap in the fence to always be positioned properly to allow passage therethrough of the saw blade at any working angle of the latter.
More particularly, in accordance with the invention, the entire turntable and support of the radial arm saw may be accurately adjusted, preferably by the operation of screw-threaded means, so that the turntable rotational axis may coincide with or may be spaced a precise distance in front of the plane defined by the work fence. Preset limit stops may be employed to define the adjustment limits of the saw turntable rotational axis relative to the fence plane.
The fence is supported on a carriage having a linear guide across the turntable rotational axis and the linear guide is fixed in relation to the basic support for the saw and its turntable carriage. Engaging cam and follower elements of the saw turntable and fence carriage coact in reponse to turntable rotation to displace the work fence on a linear path in direct proportion to angular rotation of the saw turntable, so that the fence clearance gap is always in alignment with the rotating saw blade for any angular path of movement thereof during the cutting of workpieces which are held in engagement with the fence.
The invention finds particular utility in the center line cutting of members for roof trusses which necessitates the rotational axis of the saw turntable being displaced varying distance from the fence plane.
Other objects and advantages of the invention will become apparent during the course of the following description.